Modular extrusion die tools

ABSTRACT

Modular extrusion die tools for extruding an extrudable material into an extruded article. In at least some embodiments, an extrusion die tool comprises a base, a sizing plate, a mandrel, and a die holder. When the sizing plate and mandrel are removably inserted into the base, and the base is removably inserted into the die holder, a billet of extrudable material may be injected under high pressure into the die tool. As it exits the die tool, the material is extruded into a desired shape. Because of the extreme forces to which the extrusion die tools are repeatedly subjected, some portions of the die tools can wear out relatively rapidly. Other portions, however, wear at a much slower pace. Consequently, certain portions of the die tool may need to be replaced more frequently than other portions. Because the extrusion die tools of the present invention are modular, the highly-worn portions of a die tool may be replaced without replacing the entire tool.

RELATED APPLICATION

This application is a continuation-in-part of U.S. patent application Ser. No. 10/918,596, which was filed on Aug. 13, 2004, and which is incorporated herein by reference.

BACKGROUND

Extrusion fabrication is a known process that involves forcing material, generally aluminum or aluminum alloy under a combination of heat and pressure, so as to be flowable (normally referred to as a “billet”), through an extrusion die tool to form a product having a cross section that matches the extrusion profile of the die tool. Many manufacturing processes involve extrusion fabrication. For example, extrusion fabrication is widely used in the manufacture of flat, multi-cavity aluminum tubes, which are used for small heat exchanger components in air-conditioners, condensers, and radiators.

U.S. Pat. No. 6,176,153 B1 to Maier (“Maier”) discloses a current method known in the art for manufacturing extrusion die tools, and is incorporated herein by reference, FIG. 1 shows a flow diagram of the Maier method. As shown in FIG. 1, the method begins with cutting steel in Step 10 to form the desired extrusion die tool design. In Step 10, the extrusion die tool is machine cut in a series of sub-steps from annealed (i.e., non-hardened), hot-working steel on machinery well-known in the art, such as a lathe and/or a mill, into a semi-finished state. The semi-finished state refers to the extrusion die tool being cut into the general, desired shape but not being cut to its final dimensions. Thus, a certain amount of stock metal remains on the extrusion die tool after this cutting step and will have to be removed later on in the manufacturing process.

After the extrusion die tool is cut into its semi-finished state, the die tool is hardened for the first time in Step 20 using known hardening processes. After the extrusion die tool is hardened in Step 20, the die tool is finished to its final dimensions in Step 30. In Step 30, the stock metal left on the extrusion die tool from Step 10 is ground and cut off until the die tool is shaped to the desired final dimensions (i.e., the “finished state”). As a result of the hardening process of Step 20, the extrusion die tool cannot be easily cut on a lathe or a mill in Step 30. Rather, the extrusion die tool is finished in Step 30 by a process utilizing surface grinders, polishing machines, and electric discharge machines (“EDMs”). The Maier method involves the use of both a conventional EDM and a wire EDM to make all the necessary cuts to produce a finished die tool. It will be appreciated that due to the amount of cuts performed by a conventional EDM, the use of the conventional EDM is very time consuming and costly because it utilizes an electrode, such as a copper or graphite electrode, that must be replaced for each cycle of cuts in this process.

After the extrusion die tool is finished, the extrusion die tool is coated in Step 40 by the chemical vapor deposition (“CVD”) process described in Maier. As described in Maier, the extrusion die tool is coated at pre-determined locations with a wear resistant carbidic, nitridic, boridic, and/or oxidic-coating material. After the finished extrusion die tool is coated at the desired location(s), the die tool is rehardened in Step 50 by known hardening processes. On the Rockwell C-scale of hardness (“Rc”), the die tool is hardened to a hardness of about 46-50 Rc.

Many types of extrusion die tools may be made by these methods. For example, these methods are often used to make certain “closed” extrusion die tools that are used to manufacture flat aluminum tubes for small heat exchanger components in air conditioners. Such closed extrusion die tools, such as the one shown in FIG. 3, usually consist of a comb-like mandrel 77, a sizing plate insert 72, and a bulky two-part body 70 a and 70 b that is held together with screws 74. An optional spacer plate is sometimes included to adjust the positioning of the sizing plate insert in the body of the die tool. The closed extrusion die tool is then inserted into an extrusion device, which positions the die tool so that billet is injected into enclosed injection ports 78 in the two-part body. The billet thereafter emerges from the tool in the desired shape, in this example, as small, flat tubes. Because of the extremely high forces used to extrude metal through the die tool, such closed extrusion die tools are subject to wear and must be replaced relatively frequently.

BRIEF SUMMARY

Certain embodiments of the present invention comprise a modular extrusion die tool for use in extruding an extrudable material being forced through the die tool into an extruded article. In at least some embodiments, the modular extrusion die tool comprises a base having an opening formed along a transverse axis from a first side of the base to a second side of the base, the opening defining an internal surface within the base; a sizing plate holder formed on the first side of the base along an edge of the opening; a bridge joined to the base on the second side of the base and spanning the opening, the bridge having a receiving slot formed through the bridge from a first surface of the bridge that faces away from the base to a second surface of the bridge that faces inwardly toward the opening, and the receiving slot being essentially aligned with the transverse axis; a sizing plate having an extrusion slot formed therethrough, the sizing plate configured to be removably inserted into the sizing plate holder and retained in the sizing plate holder over the opening in the base so that the extrusion slot substantially aligns with the receiving slot; a mandrel having a distal end and a proximal end, the mandrel configured to be inserted into the receiving slot and removably retained in the receiving slot so that the distal end extends beyond the second surface and is positioned adjacent to the extrusion slot to form an extrusion gap between the distal end and an edge of the extrusion slot; and a die holder having one or more die chambers formed on one side thereof, the die chamber opening outwardly to the one side of the die holder and being configured to removably receive and retain the base when the base is inserted into the die chamber, the die holder also having an injection inlet port formed on an opposite side of the die holder, the injection inlet port opening to the opposite side of the die holder, the injection inlet port being in communication with the die chamber such that the injection inlet port is in communication with the opening through the base so that when extrudable material is forced into the injection inlet port, the extrudable material flows through the injection inlet port around the bridge and through the opening in the base around the distal end of the mandrel and through the extrusion gap to form an extruded article the size and shape of which is determined by the size and shape of the slot and the size and shape of the distal end of the mandrel.

In some embodiments, the injection inlet port defines an injection inlet port wall within the die holder, the injection inlet port wall being tapered from the opening to the opposite wall to the opening in the base to funnel down the injection inlet port to the approximate size of the opening in the first side of the base. The internal surface of the opening in the base may be tapered to funnel down the opening from the second side to the first side.

In at least some embodiments, the bridge of the base extends laterally from the second side of the base beyond the internal surface of the base such that the bridge is not within the opening of the base.

Some embodiments of such an extrusion die tool further comprise a splitter plate, which is configured to be removably coupled to the bridge such that the splitter plate covers the proximal end of the mandrel when the mandrel is fully inserted into the receiving slot. The splitter plate may have two ends, each end having a leg projecting transversely to the splitter plate, and the bridge may have two ends, each end having a notch configured so that the legs of the splitter plate fits into the notches of the bridge to removably join the splitter plate to the bridge.

The splitter plate may be mounted to the die holder in the injection port such that the splitter plate covers the proximal end of the mandrel when the mandrel is inserted into the receiving slot and the base is inserted into the die chamber in the die holder. Further, the splitter plate may be removably mounted to the die holder.

In certain embodiments, the mandrel of the extrusion die tool is shaped to fit within the receiving slot such that the proximal end of the mandrel is flush with the first surface of the bridge. In other embodiments, however, the proximal end of the mandrel is not flush with the first surface of the bridge. In certain of those embodiments, the mandrel has a mandrel base on the proximal end of the mandrel that is larger than the receiving slot and the splitter plate has a recess formed therein shaped to receive the mandrel base when the mandrel is inserted into the receiving slot and the splitter plate is positioned over the bridge.

In at least some embodiments, the mandrel has a transverse axis, a longitudinal axis perpendicular to the transverse axis, and a cross axis perpendicular to both the longitudinal axis and the transverse axis, and the distal end of the mandrel has at least one tooth formed thereon, the at least one tooth having at least two undercut surfaces aligned perpendicularly to the longitudinal axis and the transverse axis of the mandrel. In some embodiments, the mandrel has two or more teeth with a gap formed between the teeth.

In some embodiments, the bridge has a recess formed on the first surface around the periphery of the receiving slot, and the mandrel has a mandrel base formed on the proximal end of the mandrel, the mandrel base being shaped to fit within the recess so that the mandrel base is flush with the first surface of the bridge when the mandrel is inserted into the receiving slot.

In at least some embodiments, the base has a tapered external surface between the first side and the second side and the die chamber in the die holder has a tapered internal surface that mates with the tapered external surface of the base so that the base can be removably inserted into the die chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a flow diagram of the method known in the prior art for manufacturing extrusion die tools;

FIG. 2 shows a flow diagram of another method for manufacturing extrusion die tools;

FIG. 3 shows an exploded view of a “closed” extrusion die tool;

FIG. 4 shows an exploded view of an embodiment of an “open” extrusion die tool;

FIG. 5 a shows a rear view of an embodiment of a base for an “open” extrusion die tool;

FIG. 5 b shows an embodiment of a mandrel that can be used with the extrusion die tools of FIGS. 3 and 4;

FIG. 5 c shows a cross-sectional view of the annular base of FIG. 5 a taken along line 5 c-5 c;

FIG. 6 shows a front view of the base of FIG. 5 a;

FIG. 7 a shows an embodiment of a sizing plate that can be used with the base of FIG. 5 a;

FIG. 7 b shows a cross-sectional view of the sizing plate of FIG. 7 a taken along line 7 b-7 b;

FIG. 8 shows a cross-sectional view of the base of FIG. 5 a along line 8-8;

FIG. 9 shows an exploded cross-sectional view of an embodiment of an “open” extrusion die tool with the base, sizing plate, and mandrel of FIGS. 5 a-8;

FIG. 10 a shows a front view of another embodiment of an extrusion die tool with the base and sizing plate of FIGS. 5 a-9;

FIG. 10 b shows a cross-sectional view of the embodiment of FIG. 10 a along line 10 b-10 b;

FIG. 10 c shows a cross-sectional view of another embodiment of an extrusion die tool;

FIG. 11 a shows a cross-sectional view of another embodiment of an extrusion die tool;

FIG. 11 b shows a perspective view of an embodiment of a die holder;

FIG. 11 c shows a cross-sectional view of the embodiment of the die holder shown in FIG. 11 b;

FIG. 11 d shows an alternative cross-sectional view of the embodiment of the die holder shown in FIGS. 11 b and 11 c;

FIG. 12 shows a front view of another embodiment of an extrusion die tool;

FIG. 13 shows a front view of an embodiment of a mandrel;

FIG. 14 shows a front view of another embodiment of a mandrel;

FIG. 15 shows a side view of the mandrel of FIG. 14;

FIG. 16 shows an enlarged sectional view of outlined portion 16 of the FIG. 13 embodiment of a mandrel;

FIG. 17 shows a cross-sectional view of a tube made by any of the extrusion die tools of FIGS. 3, 4, 9, and 11 a;

FIG. 18 shows a front view of another embodiment of a mandrel; and

FIG. 19 shows a profile view of the mandrel of FIG. 18.

DETAILED DESCRIPTION

It will be appreciated by those of skill in the art that the following detailed description of the disclosed embodiments is merely exemplary in nature and is not intended to limit the scope of the appended claims.

FIGS. 1 and 2 show flow diagrams of different methods of manufacturing extrusion die tools. The example method of FIG. 2 for manufacturing an extrusion die tool has a cutting and finishing Step 61 that both cuts and finishes annealed steel into the finished state of the desired extrusion die tool design. Thus, unlike the Maier method shown in FIG. 1, this method does not cut annealed steel into a semi-finished state, harden the semi-finished die tool, and then finish the hardened die tool into its finished state. Rather, as shown in Step 61 in FIG. 2, this method cuts and finishes annealed steel into the finished state (i.e., the die is cut to its final dimensions) of the desired extrusion die tool. Thus, this method eliminates the first hardening Step 20 of the Maier method.

Further, by virtue of annealed steel not undergoing a first hardening step, a lathe and/or a mill, instead of a conventional EDM, can now be employed in Step 61 to machine cut the extrusion die tool to its final dimensions. While a conventional EDM may still be required to make detailed cuts (i.e., cutting small grooves or channels on the die tool), the use of a conventional EDM is substantially reduced in this process. Thus, the electrode of the conventional EDM does not have to be replaced as frequently and the time devoted to the preparation of the conventional EDM is substantially reduced, if not eliminated altogether (in the event no detailed cuts are needed). As a result, the finishing of such an extrusion die tool can be completed within minutes, instead of the several-hours timeframe associated with the finishing of a die tool using a combination of conventional and wire EDMs.

Moreover, by eliminating the hardening Step 20 of FIG. 1, the method of FIG. 2 reduces the time needed for and the inherent production costs associated with the manufacturing of extrusion die tools, regardless of whether a wire EDM or a combination of conventional and wire EDMs is used to finish an extrusion die tool. Eliminating the first hardening Step 20 of FIG. 1 does not seem to have any adverse effect on the quality of the resulting extrusion die tool, and has been found to increase the life of the die tool so that it does not wear out as quickly as die tools produced from the Maier method.

Referring again to FIG. 2, instead of wasting time waiting for the steel to harden, the extrusion die tool can now be immediately coated in Step 62 and then hardened in Step 63 to complete the die tool. As already discussed above, the method also has the added benefit of allowing steel to be processed in its non-hardened, annealed state, which lends itself to easier cutting and finishing into the desired extrusion die tool design. Thus, instead of cutting annealed steel into a semi-finished extrusion die tool, hardening the semi-finished die tool, and then finishing the hardened die tool, the method shown in FIG. 2 cuts and finishes annealed steel into a finished die tool in Step 61. By cutting and finishing annealed steel, the example method eliminates the need to use certain types of equipment, such as various types of mills and grinders, and reduces, if not eliminates, the need to use conventional EDMs, to finish a hardened semi-finished extrusion die tool into a finished die tool. The elimination of such equipment, in conjunction with cutting and finishing a die tool from annealed steel, reduces machine time by as much as fifty percent, which in turn, leads to a further reduction in the inherent cost of manufacturing extrusion die tools. Steel in the annealed state is more susceptible to surface marring and thus, greater care must be exercised in its handling. For example, whereas hardened steel permits the use of a coarse-grit polishing compound, it is advisable with annealed steel to use a finer-grit compound at a lower pressure to polish the extrusion die tool in order to prevent surface marring in Step 61.

A variety of extrusion die tools can be manufactured from annealed steel using the method of FIG. 2. For example, FIG. 3 shows an exploded view of a “closed” extrusion die tool 70 used to manufacture flat aluminum tubes for small heat exchanger components in air-conditioners that can be manufactured using the method of FIG. 2. As shown in FIG. 3, the “closed” extrusion die tool comprises a two-piece die tool 70 with a male body 70 b and a female body 70 a. Male body 70 b has a comb-like mandrel insert 77 and has ports 78 that are enclosed by the exterior of the male body 70 b. The enclosed ports 78 represent the feature that distinguishes die tool 70 as a “closed” extrusion die tool. Female body 70 a has a sizing plate insert 72 with an extrusion slot 73. Screws 74 fasten together male body 70 b and female body 70 a of die tool 70. Screws 75 can be used to hold in place an optional spacer plate (not shown), which serves to adjust the height of sizing plate insert 72.

FIG. 4 shows an exploded view of an “open” extrusion die tool 80 also used to manufacture flat aluminum tubes for heat exchanger components in air-conditioners that can be manufactured using the method of FIG. 2. As shown in FIG. 4, the “open” extrusion die tool 80 has an annular base 82 that holds a sizing plate 84 with an extrusion slot 86. Further, die tool 80 has an open backside with a receiving slot 88 that retains a comb-like mandrel 90. A splitter plate 92 is used to cover receiving slot 88 and the backside of mandrel 90. The lack of ports enclosed by an exterior surface distinguishes die tool 80 as an “open” extrusion die tool.

While the two aforementioned extrusion die tools are representative of die tools that can be manufactured from the method of FIG. 2, any number of extrusion die tools can be manufactured using the method of FIG. 2. For example, closed and open die designs with integral sizing plates and mandrels can also be manufactured by this method. However, it will be appreciated that the methods described herein are merely example methods that can be used to manufacture various embodiments of extrusion die tools, but they do not limit the scope of any of those embodiments. The various embodiments of the extrusion die tools may be made according to the method of FIG. 1, the method of FIG. 2, or any other suitable method.

Referring now to FIGS. 5 through 10, there is shown another embodiment of an open modular extrusion die tool of the present invention. In this embodiment, an extrusion die tool 200 includes a base 210, a sizing plate 220, and a mandrel 230. Base 210 has a tapered external surface 211 between a first side 212 and a second side 214 of base 210 for reasons that will be described below. Base 210 has an opening 240 formed from second side 214 of base 210 toward first side 212 of base 210, generally formed along a transverse axis 215, as shown in FIG. 8. A bridge 250 is joined to second side 214 of base 210 and spans opening 240. Opening 240 defines internal surfaces 255 and 257, which are adjacent to and surround opening 240 on opposite sides of bridge 250. Internal surfaces 255 and 257 are tapered to funnel down opening 240 from second side 214 of base 210 to first side 212 of base 210 in order to facilitate extrusion of the billet, as shown in FIG. 8, FIG. 8 also shows that bridge 250 extends laterally from second side 214 of base 210 beyond internal surfaces 255 and 257 of base 210 such that bridge 250 is not within opening 240. By contrast, “closed” extrusion die tools, such as the tool shown in FIG. 3, do not have bridges that extend laterally beyond the internal surface surrounding the base's opening, but rather have bridges enclosed within the opening to form enclosed injection ports, such as ports 78 shown in FIG. 3.

Referring again to FIGS. 5 through 10, bridge 250 has an external surface 251 facing away from base 210 and an internal surface 253 facing inwardly toward opening 240. Through bridge 250, from external surface 251 to internal surface 253 and generally aligned with transverse axis 215, there is formed a receiving slot 260 into which mandrel 230 may be removably inserted. Mandrel 230 has a mandrel base 270 at its proximal end, a mandrel body 280, and mandrel teeth 290 extending from mandrel body 280 at the distal end of mandrel 230. In this embodiment, mandrel base 270 is larger than mandrel body 280 so that a portion of mandrel base 270 extends beyond the edges of mandrel body 280 to form a ledge 271 around mandrel body 280. Mandrel base 270 is larger than receiving slot 260 so that mandrel base 270 will retain mandrel 230 in receiving slot 260 by preventing mandrel 230 from sliding through receiving slot 260. When mandrel 230 is retained in receiving slot 260, the distal end of mandrel 230 extends beyond internal surface 253 of bridge 250.

Although mandrel base 270 is larger than mandrel body 280 in the embodiment shown in FIGS. 5 through 10, various other embodiments of the present invention may have a mandrel base that is not larger than its mandrel body 280, and therefore such embodiments do not form a ledge around the mandrel body. In those embodiments, as discussed herein, the sides of the mandrel body may be tapered so that the mandrel is held in position in a tapered receiving slot by interaction of the portions of the bridge forming the receiving slot and the tapering sides of the mandrel body. Alternatively, the mandrel may be held in the receiving slot in any other acceptable way, so long as the mandrel may be removably retained in the receiving slot without allowing the mandrel to slide entirely through the receiving slot.

Referring now to FIGS. 5 through 8, bridge 250 bisects opening 240, but could be positioned anywhere over opening 240, so long as receiving slot 260 of bridge 250 holds mandrel 230 over opening 240 such that mandrel body 280 and mandrel teeth 290 are within opening 240 and are exposed to billet flowing through opening 240. Although mandrel 230 is shown in FIG. 5 c having multiple mandrel teeth 290, other embodiments of mandrels may have any number of teeth or even a single tooth, so long as the one or more teeth permit extruded material to flow through the extrusion slot in the sizing plate, as described herein.

Referring now to FIGS. 5 c and 6, a sizing plate holder groove 300 is formed into base 210 along an edge of opening 240 on first side 212 of base 210. Sizing plate holder groove 300 includes a ridge 310 around the circumference of sizing plate holder groove 300 so that sizing plate 220 may be removably inserted into and retained in sizing plate holder groove 300. Sizing plate 220 rests against ridge 310 when inserted. Ridge 310 thereby prevents sizing plate 220 from pushing through opening 240 and positions sizing plate 220 within base 210. However, the sizing plate may be positioned within the base by any acceptable means, such as by the use of tabs extending from the interior of opening 240.

Formed through sizing plate 220 is an extrusion slot 320. Extrusion slot 320 is positioned on sizing plate 220 so that extrusion slot 320 aligns with receiving slot 260 and mandrel teeth 290 when mandrel 230 is inserted into receiving slot 260 and sizing plate 220 is inserted into sizing plate holder 300 (see FIG. 10 a). FIG. 9 illustrates how mandrel 230, base 210, and sizing plate 220 are joined. Sizing plate 220 may include notch 330 that corresponds to tab 340 extending from an edge of sizing plate holder groove 300. When sizing plate 220 is inserted into sizing plate holder groove 300 so that tab 340 fits in notch 330, sizing plate 220 is positioned so that extrusion slot 320 is properly aligned with mandrel teeth 290 when mandrel 230 is removably inserted into base 210. However, there are other methods of ensuring proper alignment between the extrusion slot and the mandrel teeth. For example, the sizing plate could include the tab and the sizing plate holder could include the corresponding notch. Also, although sizing plate 220 and sizing plate holder groove 300 are shown in FIGS. 6 through 9 in the shape of a circle, the sizing plate and holder could be formed into the shape of a rectangle, square, oval, pentagon, or any other suitable shape to prevent misalignment between the mandrel teeth and the extrusion slot. Those of ordinary skill in the art will recognize that other methods may be used to facilitate proper alignment between the sizing plate and the mandrel teeth of various embodiments of such extrusion die tools.

Referring again to FIG. 5 c, a recess 350 is formed into external surface 251 of bridge 250 around the periphery of receiving slot 260. Recess 350 is shaped to match the size and shape of mandrel base 270 so that, when mandrel 230 is inserted into receiving slot 260 of bridge 250, mandrel base 270 fits within recess 350 such that mandrel base 270 is flush with external surface 251 of bridge 250. However, various other embodiments have no recess surrounding the receiving slot. For example, in various embodiments having a mandrel base that is no larger than the mandrel body, a tapered mandrel may fit within a tapered receiving slot such that the mandrel is flush with the surface of the bridge without any recess formed in the bridge, as described in more detail below.

Referring now to FIG. 10 a, there is shown base 210 inserted into an annular die holder 360. Sizing plate 220 is inserted into sizing plate holder groove 300 of base 210. FIG. 10 b shows a cross-sectional view of die holder 360 and base 210 along line 10 b-10 b. Die holder 360 has formed on one of its sides a tapered die chamber 370 into which tapered base 210 may be removably inserted. On its opposite side, die holder 360 includes an injection inlet port 380, which is in communication with die chamber 370. Injection inlet port 380 defines a wall 390, which is formed in die holder 360. Wall 390 is tapered so that hot metal flowing into injection inlet port 380 is funneled down into opening 240 of base 210 when base 210 is inserted into die chamber 370. While the embodiment of FIGS. 10 a and 10 b has a single, continuous wall 390 surrounding the injection inlet port 380, the injection inlet ports of certain other embodiments may be surrounded by multiple walls, so long as the walls are configured to direct hot metal flow into an opening of a base inserted in the die chamber.

As is shown in FIGS. 8 and 10 b, opening 240 of base 210 has sloped internal surfaces 255 and 257 formed in base 210. Internal surfaces 255 and 257 are adjacent to wall 390, and may be sloped to correspond to the slope of wall 390, so that hot metal flowing into injection inlet port 380 is funneled around bridge 250 into opening 240 and then is funneled toward extrusion slot 320 in sizing plate 220 when sizing plate 220 is inserted into sizing plate holder 300. While the embodiment shown in FIG. 10 b has two internal surfaces 255 and 257 surrounding opening 240 of the base, the openings of other embodiments may be surrounded by one surface or more than two surfaces, so long as the surfaces direct hot metal flow toward the extrusion slot of the sizing plate. Similarly, the slope of the internal surfaces surrounding opening 240 need not correspond to the slope of the wall or walls surrounding the injection inlet port, so long as the surfaces surrounding the opening, the walls surrounding the injection inlet port, and the junction between the surfaces of the base and the walls of the die holder do not significantly inhibit hot metal flowing from the injection inlet port to the opening of the base and then to the extrusion slot.

Now referring to FIG. 10 c, the configuration(s) of the die chamber 370 and/or injection inlet port 380 need not be tapered as previously described. Indeed, wall 390 may comprise any configuration, provided hot metal may flow through the injection inlet port 380 and into the die chamber 370. In at least one embodiment, the wall 390 forms an angle θ where the wall 390 intersects with the base 210 when the base 210 is seated within the die chamber 370 as shown in FIG. 10 c. The angle θ may comprise any value from about 175° to about 90°, and it is contemplated that the specific value of angle θ may be selected in accordance with the particular specifications of a project.

When the die holder 360 is used in extrusion fabrication, the formation of the angle θ between the wall 390 and the base 210 serves to alter the directional flow of the hot metal flowing through the die holder 360. This change in the directional flow has proven beneficial in working with particular metals such as aluminum.

Referring back to FIG. 10 b, in operation, a hot billet is injected into injection inlet port 380 in the direction of Arrows F and flows over bridge 250 and mandrel base 270 into opening 240 of base 210. Internal surfaces 255 and 257 direct the billet through the gap between mandrel teeth 290 and the edge of extrusion slot 320 of sizing plate 220. Billet emerges from extrusion slot 320 in the desired size and shape determined by the size and shape of mandrel teeth 290 and extrusion slot 320. The product is then cut from the billet remaining in the extrusion slot by passing a blade across the outside face of sizing plate 220.

It is generally advantageous for mandrel 270 to be flush with external surface 251 of bridge 250 when mandrel 270 is inserted into receiving slot 260 of the bridge 250. The billet is injected into the injection inlet port and flows over the bridge and the mandrel base with such high pressure that any portion of the mandrel projecting above the bridge may be subjected to significant forces that can damage the mandrel 270. Therefore, in those embodiments having a mandrel 270 that is not flush with the bridge, it is desirable that the mandrel 270 be protected during injection of the billet. One way to protect the mandrel during injection of the billet is to provide a splitter plate to cover the mandrel 270 and receiving slot.

Referring now to FIG. 11 a, illustrated is an embodiment of an extrusion die tool having a base 400, a mandrel 410, and a splitter plate 420. When mandrel 410 is removably inserted into receiving slot 440 of bridge 450 on base 400, mandrel base 460 formed at the proximal end of mandrel 410 projects above bridge 450 and is therefore not flush with bridge 450. Consequently, splitter plate 420 may be used to cover mandrel base 460 to protect mandrel 410 from excessive damage from the high forces caused by billet injection.

Bridge 450 has two ends, each of which has a notch 465. Splitter plate 420 has face member 470 with two ends, and at each end is formed a leg 471 projecting transversely to face member 470. Splitter plate 420 is sized to fit over bridge 450 so that mandrel base 460 (and therefore receiving slot 440) is covered. Each leg 471 of splitter plate 420 is sized to fit into one of notches 465 when splitter plate 420 is positioned over bridge 450. Splitter plate 420 may be removably coupled to base 400 to cover mandrel base 460 when mandrel 410 is inserted into receiving slot 440. In this embodiment, face member 470 of splitter plate 420 has an indentation 425 on the side of face member 470 facing mandrel base 460 that is sized and shaped to correspond to the size and shape of mandrel base 460 such that the portion of mandrel base 460 projecting above bridge 450 fits into indention 425 in face member 470 when splitter plate 420 is coupled to base 400. Splitter plate 420 and base 400 may be removably coupled by any acceptable means, including by friction, screws, or fasteners.

As previously mentioned, in the embodiment shown in FIG. 11 a and similar embodiments, splitter plate 420 provides protection to the portion of mandrel 410 that projects above bridge 450 during the extrusion process. In various other embodiments, the mandrel base may be inserted into the receiving slot so that the mandrel base is flush with the bridge and does not project above the bridge (see FIG. 9). As discussed herein, this configuration helps to reduce the damage to the mandrel during the extrusion process.

In addition, forming the extrusion die tool such that its mandrel base is flush with the bridge also helps to prevent damage to other portions of the tool during the extrusion process. Specifically, the mandrel is subjected to very high forces when the product is cut from the billet remaining in the extrusion slot after extrusion. These forces can cause the bridge to bend, resulting in misalignment of the bridge and mandrel, increased wear and tear to the bridge and the portions of the splitter plate contacting the mandrel, and even breakage of the splitter plate. When the mandrel base is flush with the bridge (as shown in FIG. 10 b), however, a splitter plate is no longer needed.

However, even in such embodiments where the mandrel base is flush with the bridge, a splitter plate may be used to cover the mandrel base and provide additional protection to the mandrel. The face member of the splitter plate used in such embodiments need not have an indentation into which the mandrel base fits, but instead may have a flat surface that contacts the flush surfaces of the mandrel base and bridge when the mandrel is fully inserted into the receiving slot. For example, the face member of splitter plate 92 shown in FIG. 4 has no indention into which the base of mandrel 90 fits.

Referring again to FIG. 11 a, splitter plate 420 is removably coupled to base 400 to cover mandrel 410. Splitter plate 420 may also be removably coupled to a die holder such as die holder 360 in FIGS. 10 a and 10 b. In the embodiment shown in FIG. 11 a, legs 471 have tapered outer surfaces that correspond to the taper of the exterior surface 401 of base 400. Splitter plate 420 and base 400 are removably coupled to a die holder such as die holder 360 by means of the friction between the tapered surface of splitter plate 420 and base 400 and tapered wall 390 surrounding injection inlet port 380. Injection inlet port 380 is formed in die holder 360 such that the sloped portion of wall 390 is configured to receive splitter plate 420 and base 400 to hold splitter plate 420 and base 400 by means of the tapered surfaces. Although splitter plate 420 of the embodiment of FIG. 11 a is removably coupled to a die holder such as die holder 360 by friction, the splitter plate and die holder may be removably coupled by any other acceptable means, including by screws or fasteners. Further, although the splitter plate of the embodiment of FIG. 11 a has two legs, various other embodiments can include splitter plates having no legs.

Referring now to FIGS. 11 b-11 d, the splitter plate may alternatively be integrally formed with a die holder. Integration of the splitter plate with the die holder increases the strength of the die holder as a whole such that the splitter plate and die holder can more effectively withstand the high pressures exerted during the extrusion process.

A perspective view of a die holder having an integrally formed splitter plate is shown in FIG. 11 b. Annular die holder 475 comprises a first end 466, a second end 466 a and an integrated splitter plate 477. Similar to the other embodiments described herein, the second end 466 a of the die holder 475 forms a die chamber 479 into which a base (not shown) may be removably inserted as previously described. On the opposite side, the first end 466 of the die holder 475 comprises an injection inlet port 480, which is in communication with die chamber 479. Injection inlet port 480 defines wall 490, which is formed in die holder 475. Wall 490 may comprise a tapered configuration, form an angle θ relative to a base (not shown) when the base is seated within the die chamber 479, or comprise any other configuration provided that hot metal flowing into the injection inlet port 480 is allowed to flow down into the die chamber 479 (and ultimately through an opening in the base when the same is seated within the second end die chamber 479).

The integrated splitter plate 477 is positioned at or near the first end 466 of the die holder 475 and extends from wall 490 across the injection inlet port 480. Similar to the embodiment described in connection with FIG. 11 a, the integrated splitter plate 477 may be sized to fit over bridge 450 (not shown) so that mandrel base 460 (not shown) is covered. Accordingly, the integrated splitter plate 477 may be used to cover mandrel base 460 to protect mandrel 410 from excessive damage from the high forces caused by billet injection.

Irrespective of whether the splitter plate is integral to the die holder 475 or a separate component thereof, the configuration and placement of the splitter plate may be modified to facilitate efficiencies in the extrusion process. For example, the splitter plate may comprise a rectangular shape similar to the configuration of the modular splitter plate 420 shown in FIG. 11 a. Alternatively, the splitter plate may comprise rounded or curved edges.

FIG. 11 c shows a cross-sectional view of the die holder 475 taken along line A-A of FIG. 11 b comprising one example of a rounded configuration. The rounded configuration of the splitter plate reduces the overall surface area of the splitter plate as compared to a similar splitter plate having a rectangular configuration. This decreased surface area results in less resistance during the extrusion process. Accordingly, while concurrently protecting the underlying mandrel base 460, a splitter plate having a rounded or curved configuration facilitates the extrusion process by providing less resistance and therefore reducing the extrusion pressure required to manufacture the extrusion product. While these various configurations are shown in FIGS. 11 b-d in connection with the integral splitter plate 477, it is contemplated that the same may be employed in connection with any of the other splitter plate configurations described herein, including without limitation splitter plate 220.

The position of the splitter plate relative to the end of the die holder may also have an affect on the overall extrusion process and efficiencies of the same. In addition to those embodiments described herein where the splitter plate (whether modular or integral with respect to the die holder) is positioned in a substantially planar or flush configuration relative to an end of the die holder, the splitter plate may alternatively be recessed to some degree within the injection inlet port of the die holder. At least one embodiment of this recessed configuration is illustrated in FIG. 11 d. Specifically, FIG. 11 d shows a cross-sectional view of at least one embodiment of die holder 475 taken along line B-B of FIG. 11 b. In this embodiment, integral splitter plate 477 extends from wall 490 of the die holder 475 at a location offset from the first end 466 of the die holder 475. In this manner, the integral splitter plate 477 is recessed within the injection inlet port 480 and the surface of the integral splitter plate 477 is on a different plane than the first end 466 of the die holder 475.

The distance which the splitter plate is recessed within the injection inlet port 480 may be determined pursuant to the particular specifications of a project and/or to achieve optimal extrusion conditions. In the at least one example shown in FIGS. 11 c and 11 d, the surface of the integral splitter plate 477 is offset below the first end 466 of the die holder 475 a distance of about a 1/16 of an inch.

Positioning the splitter plate 477 in the recessed configuration has been found to prevent the formation of air pockets in the hot metal during the production process and have a favorable effect on production efficiency. Conventionally and as previously described herein, to form each individual extrusion die tool a continuous hot metal supply is fed into the die holder 475, which forms a billet once positioned therein. To form each individual extrusion die tool, the continuous hot metal supply is divided from the billet residing within the die holder 475 by shearing the hot metal at a location adjacent to the first end 466 of the die holder 475. As the hot metal typically comprises a pliable consistency similar to clay or moldable modeling compound, the residual hot metal within the injection inlet port 480 has the tendency to pull in the direction of the shearing force, thereby creating space (or air pockets) within the residual hot metal residing in the injection inlet port 480. When the hot metal flow is thereafter reestablished through the die holder 475 to produce the next extrusion die tool and extrusion pressure is applied, the air retained within such air pockets is forced out of the hot metal as the tool is formed, which ultimately results in a substandard end product having one or more holes.

When the splitter plate is configured in a substantially flush configuration relative to the surface of the first end 466 of the die holder 475 and the hot metal supply is sheared from the billet, the splitter plate divides the billet housed within the injection inlet port 480 into two separate portions. This division increases the likelihood that air pockets will form when the hot metal supply is sheared. Conversely, the recessed configuration of the splitter plate enables the hot metal of the billet to form a solid face within the entrance of the injection inlet port 480 when the billet is sheared from the hot metal supply. This solid face is easier to sheer from the hot metal supply without the formation of air pockets, which reduces the amount of substandard end product produced. Accordingly, the recessed configuration of the splitter plate relative to the first end 466 of the die holder 475 facilitates the efficient use of materials, thereby reducing the overall waste associated with the extrusion process and increasing production efficiency.

Referring now to FIG. 12, extrusion die tool 500 includes a die holder 510, which has a multiplicity of die chambers 520. A die tool base 530 is removably inserted into each of the multiplicity of die chambers 520. Base 530 has formed on its external surface a knob 535 that extends outwardly from base 530. On die holder 510 adjacent to each of multiplicity of die chambers 520, there is formed a knob slot 537 into which knob 535 fits when base 530 is properly inserted into die holder 510. Knob 535 and knob slot 537 may be used to properly align base 530 with die holder 510 when base 530 is inserted into one of the multiplicity of die chambers 520.

The multiplicity of die chambers in the same die holder enables increased extrusion capacity and, under certain circumstances, may decrease the physical space needed to house the manufacturing equipment. Although the embodiment of FIG. 12 includes a die holder having four die chambers, various other embodiments may include die holders having two, three, or more die chambers.

An embodiment of an extrusion die tool may include a die holder, such as die holder 360 shown in FIGS. 10 a and 10 b or die holder 510 shown in FIG. 12, which may be removably inserted into an extrusion device. The extrusion device positions the die tool for use during the extrusion process, retaining the die tool in a proper position so that the billet is injected under high pressure into the injection inlet port of the die tool. As is explained in more detail below, the billet is then pushed out of the extrusion slot of the die tool in the desired shape.

Referring now to FIG. 13, there is shown one embodiment of a mandrel that may be used, for example, in the extrusion die tools depicted in FIGS. 3, 4, 9, 10 b, and 11. In this embodiment, mandrel 600 has a base 610, a body 620 extending from base 610, and one or more teeth 630 projecting from body 620. Base 610 is larger than body 620 in that base 610 extends beyond body 620 to form a ledge 640 around body 620. Base 610 includes a first face 650 and an opposing second face 660, from which body 620 extends. Mandrel 600 also has a transverse axis 665, a longitudinal axis 670 perpendicular to transverse axis 665, and a cross axis (not shown) perpendicular to both transverse axis 665 and longitudinal axis 670.

As shown in the embodiment of FIG. 13, first face 650 of base 610 is generally planar. However, in various other embodiments, the first face of the base may be rounded or otherwise non-planar.

Body 620 is of a size and shape that fits within a receiving slot of a base of an extrusion die tool such as base 210 or base 400. Mandrel base 610 is sized to be larger than the receiving slot, so that base 610 prevents mandrel 600 from sliding through the receiving slot. Base 610 thereby holds mandrel 600 into proper position for use within the base of the extrusion die tool.

In other embodiments, the mandrel may have a base that is no larger than the body. In certain of these embodiments, the base is approximately the same size and shape as the body extending from the base. For example, FIGS. 14 and 15 show mandrel 700 having base 710, body 720, and multiple teeth 730. Base 710 includes first face 740. The sides of base 710 and body 720 are tapered such that mandrel 700 narrows from first face 740 to the portion of body 720 from which multiple teeth 730 project. As a result of the tapered sides, mandrel 700 may be held within a comparably tapered receiving slot of an extrusion die tool (not shown) by interaction of the sides of mandrel 700 with the tapered portions of the base of the extrusion die tool that define the receiving slot. Such portions of the base of the extrusion die tool may be totally tapered to correspond to the tapered sides of mandrel 700 or tapered only at a portion of the slot so long as mandrel 700 is held within the receiving slot in the proper position for use. Mandrel 700 is therefore prevented from sliding through the receiving slot. Although the embodiment shown in FIGS. 14 and 15 has tapering on all four sides of mandrel 700, other embodiments may have tapering only on either set of opposing sides.

Referring again to FIG. 13, each of one or more teeth 630 has a proximal end 632 and a distal end 634. Distal end 634 defines tip 636, which is larger than the portion of proximal end 632 to which tip 636 is attached. In the embodiment shown in FIG. 13, tip 636 is rectangular, having a length (measured along longitudinal axis 670) greater than its width (measured perpendicularly to longitudinal axis 670 along the cross axis (not shown)).

When the billet is injected into the extrusion die tool, the billet flows through the tool and is forced out of the tool through the extrusion slot, such as extrusion slot 320 of the embodiment of FIGS. 5 through 10 b. The shape of the mandrel teeth, together with the shape of the extrusion slot, determine the shape of the extruded product. For example, certain embodiments of the described extrusion die tools may be used to manufacture flat, multi-cavity aluminum tubes (see FIG. 17), which are used for small heat exchanger components in air-conditioners, condensers, and radiators. FIG. 16 shows an enlarged view of section 16 of mandrel 600 (shown in FIG. 13) having mandrel teeth 630. As shown in FIG. 16, at the distal end of each tooth 630 is a tip 636, and between tips 636 are gaps 830. Well chambers 840 are formed between teeth 630. Each tooth 630 defines two undercuts 850, formed by the overhang of tip 636 over proximal end 632 to which tip 636 is attached. In the embodiment shown in FIG. 16, two undercuts 850 of each mandrel tooth 630 are aligned along longitudinal axis 670.

When mandrel 600 is removably inserted into an extrusion die tool base, such as base 210, mandrel teeth 630 are aligned with the die tool's sizing plate extrusion slot, such as slot 320. As the billet flows through the extrusion die tool into the opening of the die tool base, the billet exits the die tool by flowing around mandrel teeth 630 and through the extrusion slot, as well as into well chambers 840, through gaps 830, and out of the extrusion slot. The flow of the billet in this manner produces an elongated tube having a number of alternating interior walls 880 and voids 890 within the tube 895 as shown in FIG. 17. The interior walls are formed by the billet flowing through the gaps between the mandrel teeth tips. However, because the tips of the mandrel teeth prevent the billet from exiting through the extrusion slot except around the mandrel or through the gaps between the teeth tips, the voids 890 are formed between the walls 880 inside the tube 895. The voids therefore have approximately the same cross-sectional shape as the shape of the corresponding mandrel teeth tips, and the exterior 897 of the tube 895 is the same size and shape as the extrusion slot in the sizing plate. As such, the size and shape of the extruded product may be changed by altering one or more of a number of variables, including the size and shape of the extrusion slot, the size and shape of the mandrel teeth, the size and shape of the mandrel teeth tips, the size of the well chambers, or the size of the spaces between the mandrel teeth tips.

Due to the extreme forces to which the extrusion die tools are repeatedly subjected, some portions of the die tools can wear out relatively rapidly. Other portions, however, wear at a much slower pace. This means that certain portions of the die tool may need to be replaced more frequently than other portions. For example, mandrels and sizing plates tend to need replacement most frequently, while certain other portions of the die tools wear out less rapidly and therefore need not be replaced as often. In some extrusion die tools (i.e., closed extrusion die tools), much or all of the tool must be replaced when certain portions of the tool become worn. However, modular extrusion die tools enable the operator to replace only the worn portions of the die tool, rather than all or most of the die tool. This saves the operator the expense of replacing more of the die tool than is necessary.

Because of the high forces to which mandrel teeth are subjected during extrusion, some teeth tend to break off from the mandrel body after repeated use, especially in smaller mandrels where the teeth are particularly thin. Increasing the thickness of the proximal ends of the teeth tends to increase the ability of the teeth to withstand the repeated high forces of extrusion and therefore tends to decrease tooth breakage. However, increasing the thickness of the proximal ends of the teeth generally decreases the size of the well chambers between the teeth, which can lead to the disruption of flow of the billet between the teeth tips, causing irregularities in wall formation.

Referring now to FIGS. 18 and 19, there is shown another embodiment of a mandrel that can be used with modular extrusion die tools. Mandrel 900 has base 910, body 920, and a multiplicity of teeth 930. Each of multiplicity of teeth 930 has proximal end 940 and a distal end forming tip 950. As shown in FIG. 18, proximal end 940 has a length along a longitudinal axis 960 that is the same as the length of tip 950 along longitudinal axis 960. However, as shown particularly in FIG. 19, tip 950 is wider along a cross axis 965 (as measured perpendicularly to longitudinal axis 960 and transverse axis 963) than proximal end 940 of one of multiplicity of teeth 930. Consequently, each of multiplicity of teeth 930 defines two undercuts 970, as shown in FIG. 19. Two undercuts 970 are formed by the overhang of tip 950 over proximal end 940 to which tip 950 is attached. In the embodiment shown in FIGS. 18 and 19, two undercuts 970 of each of multiplicity of teeth 930 are aligned along cross axis 965 (and therefore aligned perpendicularly to longitudinal axis 960 and transverse axis 963). This allows for an increase in the size of proximal ends 940 of teeth 930, leading to an increase in strength of the teeth and a decrease in tooth breakage. However, the greater thickness of proximal ends 940 in most cases requires a reduced size of the well chambers between teeth 930, which can lead to disruption of billet flow. Undercuts 970 permit additional billet to flow around teeth 930 to compensate for any reduced billet flow through the smaller well chambers.

The embodiments disclosed herein can be manufactured utilizing the method shown in FIG. 2. Referring back to FIG. 2, a hot-working steel can be used in Step 61 to create the male body 70 b and female body 70 a of closed die tool 70 and annular base 82 of open die tool 80. Hot-working steels provide a combination of high-temperature strength, wear resistance, and toughness that is ideal for extrusion die tools. An example of hot-working steel employed in this example method of manufacturing portions of an extrusion die tool is NU-DIE® V (AISI H13) hot-working steel, which has a typical chemical composition by weight percentage of the total amount of the composition of: 0.40% Carbon; 0.35% Manganese; 1.00% Silicon; 5.20% Chromium; 1.30% Molybdenum; and 0.95% Vanadium, with Iron comprising the remaining composition (approximately 90.80%). While one type of hot-working steel is provided, any type of hot-working steel, which has typical chemical composition ranges by weight percentage of the total amount of the composition of: 0.32-0.55% Carbon; 0.3-1.5% Manganese; 0.20-1.5% Silicon; 1.1-5.50% Chromium; 0.5-1.50% Molybdenum; and 0.13-1.2% Vanadium, with Iron comprising the remaining composition, can be used, as can any other steel with like properties.

Still referring to FIG. 2, a high-speed steel can be used to manufacture mandrels and sizing plates of the various embodiments of the extrusion die tools. High-speed steels are high alloy, W-Mo—V—Co bearing steels that are normally used in high-speed cutting tools that can withstand the high extreme heat generated at the cutting edge. An example of a high-speed steel that can be used to manufacture mandrels and sizing plates is CPM REX 76® (AISI M48) high-speed steel, which has a typical chemical composition by weight-percentage of the total amount of the composition of: 1.5% Carbon; 0.30% Manganese; 0.30% Silicon; 3.75% Chromium; 3.10% Vanadium; 9.75% Tungsten; 5.25% Molybdenum; 8.50% Cobalt; and 0.06% Sulfur, with Iron comprising the remaining composition (approximately 67.49%). While one example of high-speed steel is provided, any type of high-speed steel, which has typical chemical composition ranges by weight-percentage of the total amount of the composition of: 0.55-2.3% Carbon; 0.3-0.4% Manganese; 0.3-0.4% Silicon; 3.75-4.50% Chromium; 1.0-6.5% Vanadium; 1.5-18.0% Tungsten; 0-9.5% Molybdenum; 0-12.0% Cobalt; and trace amounts of Sulfur, with Iron comprising the remaining composition, can be used. Further, the mandrels and sizing plates could also be manufactured from hot-working steel or any other steel that has similar properties to high-speed and hot-working steels.

After Step 61 is completed, the desired parts of the extrusion die tool may be coated with a wear resistant coating in Step 62 using known coating processes at high temperatures that, by virtue of the high temperatures (i.e., temperatures that fall in the range of approximately 1000-1300° F.) at which they are conducted, serve to both coat and partially harden the steel. For example, the CVD coating process disclosed in Maier can be used to coat the desired parts of the extrusion die tool. The CVD coating is prepared from a coating material selected from the group containing titanium carbide, titanium nitride, titanium boride, vanadium carbide, chromium carbide, aluminum oxide, silicon nitride, and combinations thereof; and the coating is applied in a CVD process, preferably at temperatures in the range of 1200° F.-1300° F., to the surface of the desired portions of the extrusion die tool. Thermally-activated CVD is known in the art for the production of single crystals, the impregnation of fiber structures with carbon or ceramics, and generally for the deposition of thin layers, either by growth onto a surface or by the diffusion of borides, carbides, nitrides, and/or oxides. By virtue of the aforementioned coating and thermally-activated CVD coating step, a wear-resistant layer is provided for the coated portions of the extrusion die tool, which uniformly, regularly, and adhesively covers the coated portions. While the entire extrusion die tool itself can be coated, it is more cost-effective to coat only certain portions of the die tool (e.g., the mandrel). While this method uses a CVD coating process, any number of coating processes can be used.

Following the coating step, the coated and uncoated portions of the extrusion die tool are hardened using known hardening processes in Step 63. For example, one hardening process known in the art first involves heating the coated and uncoated portions of the extrusion die tool to a temperature of at least 100° F. above the critical or transformation point of its component steel, a point also known as its decalescence point, so that the steel becomes entirely austenitic in structure (i.e., a solid solution of carbon in iron). The coated and uncoated portions of the extrusion die tool steel are then quenched. The quenching process suddenly cools the coated and uncoated portions of the die tool at a rate that depends on the carbon content, the amount of alloying elements present, and the size of the austenite, to produce fully-hardened steel. Following quenching, the resulting extrusion die tool is tempered in order to reduce the brittleness in its hardened steel and to remove the internal strains caused by the sudden cooling associated with quenching. The tempering process consists of heating the quenched, coated and uncoated portions of the extrusion die tool by various means, such as immersion in an oil, lead, or salt bath, to a certain temperature, which may range from 1000-1200° F. for hot-working or high-speed steel, and then slowly cooling the die tool. In this method, the portions of the die tool cut and finished from hot working steel are hardened to about 46 to 50 Re, and the portions cut and finished from high-speed steel are hardened to about 53 to 56 Re. This is just one hardening process known in the art that can be used in this method. Any other type of hardening process can be utilized in association with this method.

As already explained, this example method of manufacturing reduces the number of steps, the amount of time, and the corresponding cost of manufacturing extrusion die tools. This can be further seen by comparing and contrasting how one would manufacture a mandrel using the Maier method and the example method described above. In particular, and in reference to FIG. 1, the Maier method requires: (a) six discrete cutting operations in Step 10, which include one lathe-cutting operation and five mill-cutting operations; (b) hardening in Step 20; (c) eight discrete finishing operations in Step 30, which include four surface grinding operations, one conventional and two wire EDM operations, and a polishing operation; (d) coating in Step 40; and (e) rehardening the (now coated) mandrel in Step 50, for a total of seventeen process steps. In contrast, and in reference to FIG. 2, the example method of manufacturing utilizes: (a) ten discrete cutting and finishing operations in Step 61, which include one lathe-cutting operation, two surface grinding operations, three mill-cutting operations, two wire EDM operations, a chamfering operation, and a polishing operation; (b) coating in Step 62; and (c) hardening the coated extrusion die tool in Step 63, for a total of twelve process steps, i.e., a five-step reduction relative to the Maier method. Further, as already explained, the elimination of a hardening step and the reduced use or elimination of the conventional EDM reduces machining time by approximately fifty percent.

This method of manufacturing reduces the number of steps involved in manufacturing extrusion die tools and, accordingly, the time and cost involved in manufacturing these tools. This reduction in time and cost arises primarily from the elimination of a first hardening step in the Maier method of manufacturing extrusion die tools. The elimination of the first hardening step not only saves the amount of time that it would take to harden the semi-finished die tool, but also decreases the use of certain types of equipment in the manufacturing process, such as mills and various types of surface grinders, and may eliminate entirely the use of a conventional EDM from the manufacturing process. Elimination of a conventional EDM eliminates the need for and the concomitant preparation time and cost associated with the electrode required in a conventional EDM. Further, the exclusive use of a wire EDM in the method, in lieu of the combination of conventional and wire EDMs, permits final finishing to be completed within minutes, instead of several hours. Thus, this example method substantially reduces the amount of time needed to manufacture an extrusion die tool.

While several embodiments of extrusion die tools and mandrels have been described in considerable detail herein, the embodiments are merely offered by way of non-limiting examples of the invention. It will be understood by those skilled in the art that various changes and modifications may be made, and equivalents may be substituted for elements thereof, without departing from the scope of the invention. The embodiments disclosed herein should in no way be limited to the methods of manufacturing or the extruded products disclosed herein. It is intended that the invention will include, and this description and the appended claims will encompass, all modifications and changes apparent to those of ordinary skill in the art. 

1. A modular extrusion die tool for use in extruding a material forced therethrough into an extruded article, comprising: a base comprising an opening formed along a transverse axis from a first side of the base to a second side of said base, the opening defining an internal surface within the base; a sizing plate holder formed on the first side of the base along an edge of the opening; a bridge joined to the base on the second side of the base and spanning the opening, the bridge having a receiving slot formed through the bridge from a first surface of said bridge that faces away from the base to a second surface of the bridge that faces inwardly toward the opening, and the receiving slot being essentially aligned with the transverse axis; a sizing plate having an extrusion slot formed therethrough, the sizing plate configured to be removably inserted into the sizing plate holder and retained therein over the opening in the base so that the extrusion slot substantially aligns with the receiving slot; a mandrel having a distal end and a proximal end, the mandrel adapted for insertion into the receiving slot such that the distal end extends beyond the second surface and is positioned adjacent to the extrusion slot to form an extrusion gap between the distal end and an edge of said extrusion slot; and a die holder having a first end, a second end and an interior extending therebetween, the interior comprising at least one die chamber positioned adjacent to the second end of the die holder and configured to removably receive and retain the base therein, and the first end of the die holder comprising an inlet port in communication with the die chamber.
 2. The die tool of claim 1, wherein the inlet port defines an inlet port wall within the die holder.
 3. The die tool of claim 2, wherein the inlet port wall is tapered from the first end of the die tool to the opening in the base such that the inlet port is funneled down to the approximate size of the opening in the first side of said base.
 4. The die tool of claim 2, wherein the inlet port wall forms an angle of between about 135° and about 90° with the second side of the base.
 5. The die tool of claim 2, wherein the internal surface of the opening in the base is tapered to funnel down the opening from the second side of the base to the first side of the base.
 6. The die tool of claim 1, further comprising a splitter plate adapted to be removably coupled to the bridge such that the splitter plate covers the proximal end of the mandrel when the mandrel is fully inserted into the receiving slot.
 7. The die tool of claim 1, wherein the die holder further comprises a splitter plate mounted to the die holder in the inlet port such that the splitter plate covers the proximal end of the mandrel when the mandrel is inserted into the receiving slot and the base is inserted into the die chamber in the die holder.
 8. The die tool of claim 6, wherein the first end of the die holder comprises an exterior surface positioned along a plane and when the splitter plate is removably coupled to the bridge, the splitter plate is recessed within the inlet port such that the splitter plate does not meet the plane of the exterior surface of the die holder.
 9. The die tool of claim 7, wherein the first end of the die holder comprises an exterior surface positioned along a plane and the splitter plate is recessed within the inlet port such that the splitter plate does not meet the plane of the exterior surface of the die holder.
 10. The die tool of claim 6, wherein the splitter plate comprises a rounded configuration.
 11. The die tool of claim 7, wherein the splitter plate comprises a rounded configuration.
 12. The die tool of claim 7, wherein the mandrel is shaped to fit within the receiving slot such that the proximal end of the mandrel is flush with the first surface of the bridge.
 13. The die tool of claim 7, wherein the mandrel has a transverse axis, a longitudinal axis perpendicular to the transverse axis, and a cross axis perpendicular to both the longitudinal axis and the transverse axis, and the distal end of the mandrel has at least one tooth formed thereon, the at least one tooth having at least two undercut surfaces aligned perpendicularly to the longitudinal axis and the transverse axis of the mandrel.
 14. The die tool of claim 1, wherein: the bridge has a recess formed on the first surface around the periphery of the receiving slot; and the mandrel has a mandrel base formed on the proximal end of the mandrel, the mandrel base adapted to fit within the recess so that the mandrel base is flush with the first surface of said bridge when the mandrel is inserted into the receiving slot.
 15. The die tool of claim 10, wherein: the splitter plate has two ends, each end having a leg projecting transversely to the splitter plate; and the bridge has two ends, each end having a notch configured so that the legs of the splitter plate fits into the notches of the bridge to removably join the splitter plate to the bridge.
 16. The die tool of claim 7, wherein: the base has an external surface between the first side and the second side and the external surface is tapered; and the die chamber in the die holder has a tapered internal surface that mates with the tapered external surface of the base so that the base can be removably inserted into the die chamber.
 17. A modular extrusion die tool for use in extruding a material forced therethrough into an extruded article, comprising: a base comprising an opening formed along a transverse axis from a first side of the base to a second side of said base, the opening defining an internal surface within the base; a sizing plate holder formed on the first side of the base along an edge of the opening; a bridge joined to the base on the second side of the base and spanning the opening, the bridge having a receiving slot formed through the bridge from a first surface of said bridge that faces away from the base to a second surface of the bridge that faces inwardly toward the opening, and the receiving slot being essentially aligned with the transverse axis; a sizing plate having an extrusion slot formed therethrough, the sizing plate configured to be removably inserted into the sizing plate holder and retained therein over the opening in the base so that the extrusion slot substantially aligns with the receiving slot; a mandrel having a distal end and a proximal end, the mandrel adapted for insertion into the receiving slot such that the distal end extends beyond the second surface and is positioned adjacent to the extrusion slot to form an extrusion gap between the distal end and an edge of said extrusion slot; and a die holder having a first end, a second end, an interior extending therebetween and a splitter plate, the interior comprising at least one die chamber positioned adjacent to the second end of the die holder and configured to removably receive and retain the base therein, the first end of the die holder comprising an inlet port in communication with the die chamber, and the splitter plate mounted to the die holder in the inlet port such that the splitter plate covers the proximal end of the mandrel when the mandrel is inserted into the receiving slot and the base is inserted into the at least one die chamber of the die holder.
 18. The die tool of claim 17, wherein the first end of the die holder comprises an exterior surface positioned along a plane and the splitter plate positioned within the inlet port such that when the splitter plate is removably coupled to the bridge, the splitter plate does not meet the plane of the exterior surface of the die holder.
 19. The die tool of claim 17, wherein the splitting plate comprises a rounded configuration.
 20. The die tool of claim 17, wherein the die holder has a plurality of die chambers.
 21. The die tool of claim 17, wherein at least one portion of the modular extrusion die tool is formed from an annealed high-speed steel having a chemical composition comprising one or more of: Manganese, Silicon, Chromium, Vanadium, Tungsten, Molybdenum, Cobalt, and Sulfur.
 22. The die tool of claim 24, wherein at least one portion of the modular extrusion die tool is formed from a hot-working steel having a chemical composition comprising one or more of: Manganese, Silicon, Chromium, Vanadium, and Molybdenum. 